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Guidelines for Growing Hazelnuts in New Zealand – Bulletin 1: Introduction Page 1 of 5
Guidelines for Growing Hazelnuts in New Zealand
Bulletin 1: An introduction to growing hazelnuts
in New Zealand
Murray Redpath. May 2016
Introduction
Hazelnuts have been grown commercially in
New Zealand since the 1980s, and at present
(2016) orchards are present in all regions from
Waikato to Southland. With good management
and careful planning at setup, commercial
operations may be able to supply domestic
demand and possibly export hazelnuts from
New Zealand to global markets.
This bulletin provides a background on the
hazelnut industry in New Zealand and globally,
and identifies key factors in establishing a
commercially viable hazelnut orchard.
Landowners planning to plant hazelnuts should
use the "Guidelines for growing hazelnuts in
New Zealand" series of bulletins to guide them
through selecting the most appropriate land,
varieties and management systems. Consult
local growers and consultants to source suitable
advice and services applicable to your region.
Fig. 1: Mature hazelnut orchard, Canterbury
Hazelnut species
The commercial hazelnut industry is based on
selections of Corylus avellana, a species of wind
pollinated shrubs or small trees native to
temperate areas of Europe and Asia Minor. The
genus Corylus (family Betulaceae) consists of
about 9 deciduous species naturally occurring in
temperate forest areas across Europe, the
Middle East, Asia, and North America. Up to 25
species have been described but modern
taxonomy usually recognises 5 shrub and 4 tree
species.
Environmental requirements
Commercial hazelnuts require a mild temperate
climate. The main hazelnut growing areas in the
northern hemisphere are characterised by mild
summers and cool winters without extremes of
heat or cold. Key temperature characteristics
are:
average annual temperature 12˚C to 16˚C
maximum temperature 35 to 36˚C
minimum temperature -8 to -10˚C
chilling of 600 to 1200 hours (depending on
variety)
Hazelnut trees have soft leaves and do not
tolerate extreme heat, wind or moisture stress.
In New Zealand conditions, good shelter is
essential.
Ideal annual rainfall is 800 to 1000 mm, with rain
evenly spread throughout the growing season.
Locations with rainfall well distributed up until
February may not require irrigation. Locations
that experience prolonged periods of dry
weather between November and the end of
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 1: Introduction Page 2 of 5
January should install irrigation, especially if the
soils are free draining (sandy or stony). Water
requirements are estimated at about 1 to
1.5 megalitres of water per hectare per season
for every 150 mm of annual rainfall less than
900 mm.
Warm dry weather over the harvest period (late
February to early April in most areas of New
Zealand) is advantageous. Dry weather lets
husks dry quickly so that nuts fall free, the
moisture content of the harvested nuts is low,
,and dry ground conditions favour easy
machinery operation and clean nuts.
Out of season frosts in November and
December have caused hazelnut crop losses in
parts of New Zealand. Temperatures recorded in
orchards affected by frost damage in the South
Island suggest that air temperatures of -2 to -3˚C
may be sufficient to cause damage to nut
clusters at this time. However, damage has
been inconsistent, both within orchards and
regions
Commercial hazelnut orchards require a fertile,
well drained soil, ideally with a pH of 6.0 to 6.5
Hazels have a fibrous root system with most of
the feeding roots in the top 60 cm of soil but
deep soils allow the roots to exploit a greater soil
volume. Land Use Class 1 and 2 soils are ideal
and usually need very little modification. Class 3
soils will usually need extra management such
as additional fertiliser, drainage (wet soils),
ripping (clay soils and soils with a pan within the
soil profile) or additional irrigation (free draining
sandy or stony soils with a low water holding
capacity). For successful harvesting using
machinery, the orchard must be flat or gently
sloping..
World hazelnut production
Hazelnuts are the one of the five most
commonly traded nut crops worldwide, along
with almonds, walnuts, pistachios, and cashews.
The average annual world production (2009-
2013 FAO data) is approx. 830,000 tonnes (in-
shell). World production of hazelnuts increased
7.7% in the ten years from 2003 to 2013 (FAO
data) but the total hazelnut crop continues to
fluctuate widely (Fig. 2), affected by a strong
biennial bearing pattern and the dominant
influence of the Turkish crop. Turkey is the
largest producer with approximately 74% (64-
78% range) of world production. Italy is the
second largest producer (12-16%) followed by
Spain, USA, Georgia, and Azerbaijan
(approximately 3% each).
New hazelnut plantations have been established
over the last 15 years in many countries with
suitable climates such as Chile, Iran, Argentina,
Romania and Australia. Increasing demand and
improved profitability have also encouraged new
plantings in countries with an existing industry,
such as France, Georgia and the USA.
Fig. 2: World hazelnut production 1999 - 2013 (1000
tonnes). Data from FAO.
Hazelnuts in New Zealand
A small-scale hazelnut industry has developed
in New Zealand over the last 40 years.
Hazelnuts were introduced into New Zealand by
early European settlers but were not grown
commercially until the 1980's, when interest in
new orchard crops led to small scale planting of
hazelnuts and other nut crops . Early
development was promoted by the NZ Tree
Crops Association (NZTCA) working closely with
the Crop Division of the Department of Scientific
and Industrial Research (DSIR). Early trials were
promising. A trial planted at the Appleby
Research Orchard in Nelson was assessed for
yield from 1970 to 1975 and one cultivar
400
500
600
700
800
900
1,000
1,100
1,200
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 1: Introduction Page 3 of 5
(incorrectly labelled as Barcelona but later
renamed „Appleby‟) yielded an average of
10.3 kg per tree per year over that period. This
equated to a crop of over 4 tonnes per hectare
based on the spacing used in that trial. This is
an excellent crop by international standards.
Fig.3: Hawke's Bay orchard, 1989. The trees are 4
years old.
A visit in 1981 by Dr Maxine Thompson from
Oregon State University helped to focus the
research on finding a nut with high quality
kernels suited to the blanched kernel trade. The
aim was to develop a nut that could fetch a
premium price in local and international markets.
Nut quality assessments by the Hazelnut Action
Group, part of the NZTCA, identified a New
Zealand selection, Whiteheart, as being well
suited to the blanched kernel market. Research
carried out at Lincoln University by Dr. David
McNeil and others confirmed the excellent
kernel qualities of the Whiteheart variety and this
variety was recommended for planting in
commercial hazelnut orchards.
Interest in nut crops grew through the late
1990‟s. The Southern Nut Growers Association
was set up in 1993 to commercialise nut
production, working closely with the Hazelnut
Action Group. In 2002, the Southern Nut
Growers Association split into specific nut
groups and the Hazelnut Growers Association of
New Zealand was formed. In the late 1990‟s the
Crops for Cool Climates project in Southland
identified hazelnuts as a crop with commercial
potential for southern regions stimulating small-
scale plantings on commercial sheep farms in
Southland and Otago.
The New Zealand hazelnut industry
The 2007 Agricultural census revealed that New
Zealand had just over 400 hectares of land
planted in hazelnuts. These plantings are
dominated by the Whiteheart variety. The main
area of hazelnut production at present (2016) is
Canterbury, followed by Otago (including Central
Otago), Nelson, Southland and Marlborough.
Most hazelnut plantings are on small blocks of
land where owners are retired or have other
sources of income.
The main group representing hazelnut growers
is the Hazelnut Growers Association of New
Zealand (HGANZ). The Hazelnut Growers
Association has the following objectives:
a) Encourage the planting of hazelnut
trees, establishing trial areas for fruit
and/or timber production including the
establishment of gene banks.
b) Promote, research and encourage a
domestic and overseas export trade for
hazelnuts.
c) Promote and commission scientific
research, including plant breeding, in all
matters relative to hazelnuts.
d) Facilitate for the benefit of members the
results of all scientific investigation,
technical and practical information about
hazelnuts.
e) Promote and provide for members,
conferences, field days, workshops and
any other training methods to further
members‟ knowledge about the growing
and production of hazelnuts.
f) Promote an active liaison with the
appropriate Research Organisations and
Nut and Tree Associations in New
Zealand and relevant International
Associations.
The HGANZ has one summer field day each
year plus a weekend gathering in June. The
AGM is held during the June weekend
gathering. Information is disseminated via the
website (www.hazelnut-growers.org.nz) and a
quarterly newsletter.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 1: Introduction Page 4 of 5
Fig. 4: HGANZ members touring a local orchard.
Growers sharing their experience is an effective
method of disseminating information.
New Zealand has a wide range of processors
ranging from The Hazelnut Company, which has
a medium sized processing plant in Canterbury,
to smaller grower-processors who sell through
Farmers Markets and small local retail outlets.
Many also offer internet sales. Internet sales
have seen small quantities of New Zealand
hazelnuts exported to Australia, the USA, and
Europe.
Markets
Most hazelnuts (95%) are traded as kernels.
Despite increased reporting of the health
benefits of eating nuts, most hazelnut kernels
(95%) are still used in chocolate, baking or
confectionery.
Globally, Europe is the largest market for
hazelnuts. Germany is the largest single
European market, followed by Italy, Belgium and
Switzerland. In recent years, Italy and Spain
have become net importers of hazelnuts.
The local New Zealand market for hazelnuts is
small but increasing. Imports amount to between
200 and 250 tonnes per annum (Fig. 5).Most
hazelnuts are imported from Turkey but large
quantities are also imported from the USA, Italy
and Australia (nuts which appear to have been
imported from Australia are probably re-exports
of hazelnuts imported from other countries).
Fig. 5: NZ Hazelnut Imports (kg)and Average Per
Kilogram Value of Imported Kernels($NZ/kg) 1994 -
2011. Data from Statistics NZ
There are no accurate figures for local
production but it is estimated to be less than 100
tonnes per year. The trees on the 400 hectares
(approx.) already planted, once in full
production, should be capable of producing
between 600 and 1200 tonnes per annum. This
exceeds the current volume of hazelnut imports.
New large-scale plantings would therefore need
to plan to supply export markets.
Potential export markets exist in Australia and
Asia. Hazelnuts form a small part of the
Australian nut industry with an estimated 300
hectares planted by 2012. Annual imports of
hazelnuts into Australia amount to about 100
tonnes in-shell and 2000 tonnes of kernel,
double the anticipated domestic crop. There
may be an opportunity for New Zealand
hazelnuts to replace some of the hazelnuts
currently imported into Australia.
In China, in-shell hazelnuts are sold as a high
value snack item. Consumers prefer nuts which
have been partly cracked (allowing the shell to
be broken easily by hand) then soaked in
flavoured brine. The Oregon hazelnut industry
is a significant supplier of in-shell hazelnuts into
the world market and China is now the largest
market for the Oregon crop.
$0.00
$2.00
$4.00
$6.00
$8.00
$10.00
$12.00
$14.00
$16.00
$18.00
0
50,000
100,000
150,000
200,000
250,000
300,000
In-shell Kernels Av. kernel value
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 1: Introduction Page 5 of 5
Economics
The key influences on the economics of
hazelnut production are yield, market price, and
the scale of operations. Both high nut quality
and high yields are necessary for profitable
hazelnut growing and are achieved through:
choice of suitable climate and soils
choice of suitable varieties for the
environment and markets
appropriate planting system (suitable
nursery stock, orchard layout and early
training)
good orchard management techniques
(pruning, soil nutrient management, orchard
floor management, irrigation)
The yields achieved in hazelnut orchards are
variable. While orchards in Oregon expect to
yield around 2.5 to 3 tonnes/ha, average yields
in countries like Turkey, with less intensive
orchard management, fall below 1.5 tonnes/ha.
Early production is an important factor in
economically viable production. Hazels should
have a small crop in the third year after planting,
with the first commercial harvest in the fourth or
fifth year. Growers should plan to harvest 1
tonne/ha by year 6 and 2.5 tonnes/ha by year
10. These yields have been achieved by New
Zealand growers with good management in
suitable environments. Gross margins for well-
managed hazelnut orchards in Australia,
Oregon (USA) and Italy are commonly in the
range $4000 to $7000/ha.
Costs of establishing a hazelnut orchard vary
according to how much development work
(shelter, irrigation, land preparation) is required,
ranging from about $8500/ha (established
shelter, no irrigation required), up to $25,000
starting with bare undeveloped land requiring
significant modification.
Useful websites:
Tasmanian Government Department of Primary Industries, Parks, Water & Environment (DPIPWE):
Hazelnuts Gross Margin & Profitability Analysis.
dpipwe.tas.gov.au/Documents/Hazelnuts-GM---Profitability-Analysis.xls
Oregon State University.https://catalog.extension.oregonstate.edu/topic/agriculture/hazelnut-production
Hazelnut Growers of Oregon: www.oregonhazelnuts.org.
The “Guidelines for Growing Hazelnuts in New Zealand” bulletins were produced by the Hazelnut
Growers Association of NZ with financial assistance from the Ministry for Primary Industries Sustainable
Farming Fund and the NZ Tree Crops Association.
Murray Redpath is Chairman of the Hazelnut Growers Association of NZ.
All photographs: Murray Redpath
Disclaimer
While the author has taken all reasonable skill and care in assessing the accuracy of the information in this report, none of the
organisations involved accepts any liability, whether direct, indirect or consequential, arising out of the provision of information within
this report.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 1 of 9
Guidelines for Growing Hazelnuts in New Zealand
Bulletin 2: Hazelnut Varieties
Murray Redpath. May 2016
Selecting the right variety to suit the markets
that a grower plans to supply is a critical factor
for developing a profitable hazelnut orchard.
Most markets have specific requirements in
terms of nut or kernel size and kernel texture,
shape, taste, and blanching and/or roasting
ability. To profitably supply the chosen
markets, growers also need varieties that are
able to deliver high yields regularly from an
early age.
Hazelnuts are sold into two main markets:
kernel and in-shell. Nut quality requirements
differ between these two markets.
In-shell Markets
The in-shell market uses nuts that:
are large ( >18 mm shell diameter) with
attractive shells
have very little or no fibre on the kernel
have plump, crisp kernels when dried
are not susceptible to the development of
mould on the kernels
Fig. 1: In-shell nuts for sale, Oregon, USA.
Kernel Markets
Most hazelnuts are traded as kernels, to be
used as raw nuts for snacking or further
processed for use in confectionary, baked
goods, nut butters or other processed
products. Preferred kernel size is usually in the
11 to 15 mm range.
The kernel market is further divided into trade
in unblanched and blanched kernels. Hazelnut
kernels are covered with a brown skin, the
pellicle, which varies in appearance and ease
of removal. This blanching process usually
involves lightly roasting kernels for 10 to 15
minutes at 135 °C to 150 °C and rubbing or
brushing them.
The kernel market typically requires nuts that
have:
round nut shape with thin shells that are
easy to crack
round kernel with a strong hazel flavour
thin pellicle with little or no fibre cover
crisp texture when dried
good storage ability to prolong shelf life
In addition, the blanched kernel market
requires kernels that have a pellicle that is
easily removed by heat.
Fig.2: Unblanched kernels (Whiteheart variety)
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 2 of 9
Fig. 3: Blanched kernels (Whiteheart variety)
Other factors
Other factors to consider when selecting
varieties are:
yield potential
percent kernel
level of defective nuts
tree vigour and health
Varieties vary in their ability to crop heavily
every year. International studies show that
Barcelona has a high yield potential (i.e. crops
heavily wherever there are suitable growing
conditions) whereas Merveille de Bollwiller has
a low yield potential. Barcelona and
Whiteheart are known to have a strong
tendency towards biennial bearing (i.e. they
alternate between heavy crops and light crops)
whereas Tonda di Giffoni tends to crop well
every year.
Commercial varieties should have a high ratio
of kernel weight to nut weight (percent kernel),
to maximise the yield of saleable kernel per
tonne of nuts harvested. This ratio is
influenced by the thickness of the shell and the
amount of kernel shrinkage during drying.
Most nut processing companies have limits on
the level of defective nuts or kernels allowed.
The varieties selected must be able to yield a
crop that can meet those quality standards.
Some varieties have a tendency to develop
mould on the kernels or have thick corky fibre
on the kernels. These problems increase if
there is wet weather at harvest time.
Unfortunately the list of varieties that develop
mould contains some of the most productive
varieties such as Tonda di Giffoni.
Nut quality problems, such as kernel
shrivelling, increase in high yielding varieties
with larger nuts (e.g. Barcelona and Ennis)
when these are grown in less than ideal
climatic conditions. These problems are less
common in varieties with smaller nuts.
Round nuts are easier to crack and process
successfully. Varieties with elongated nuts,
such as Kentish Cob, are usually restricted to
small niche markets.
Varieties will only reach their full potential yield
if they are grown in well managed orchards
and are suited to the local growing
environment. Hazels are adapted to a moist
temperate climate and they hate extremes of
heat or cold. Later flowering varieties have
greater chilling requirements and yields may
be affected by a lack of winter chilling in
warmer northern areas. Varieties that come
into leaf early (e.g. Lansing, Tonda di Giffoni)
may be damaged by severe spring frosts when
grown in colder southern areas.
Many of the main hazelnut varieties grown
commercially overseas were imported into
New Zealand over 30 years ago. Evaluation of
these varieties has shown that Barcelona,
Tonda Romana, and Whiteheart have potential
to produce commercial crops of hazelnuts with
kernels that meet international quality
standards. Ennis and Tonda di Giffoni have
performed well in some orchards but more
research is needed to solve problems with nut
quality before these varieties can be
recommended for widespread planting in
commercial orchards.
Polliniser varieties are planted for pollen
production, and nut quality and yield are
secondary considerations. Most polliniser
varieties used in New Zealand produce large
nuts suited to the in-shell market. Many are
cracked and used to produce hazelnut oil or
hazelnut paste. Some varieties, such as
Alexandra, have nuts that are difficult to crack
and yield poor quality kernels.
Photographs accompanying the descriptions
illustrate the main nut characteristics (size,
shape, fibre and degree of blanching).
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 3 of 9
Commercial Varieties
Barcelona
An old cultivar widely distributed in Western
Europe, probably originating in Spain, and the
main cultivar grown in Oregon, USA for the
last century. It is very vigorous, forming a
large spreading tree. The husk, one third
longer than the nut, opens and sheds the nut
freely. Barcelona is very resistant to big bud
mites. It is susceptible to bacterial blight and is
often affected by “brown stain” which causes a
large number of misshapen nuts. It flowers
mid-season. Suitable pollinisers are Butler,
Lansing, and Merveille de Bollwiller.
Barcelona is very productive, yielding a
medium to large dark brown nut with a shell of
medium thickness yielding 39-43% kernel by
weight. The kernel often has some corky fibre
attached but blanches moderately well with a
good flavour.
Barcelona requires good orchard management
and warm dry summers to produce good
quality nuts.
Fig.4: Barcelona variety –
in-shell, unblanched kernel, blanched kernel
Ennis
Ennis was developed in Washington, USA,
and was introduced into commercial
production around 1940. It is probably a cross
between Barcelona and Daviana. It was
selected primarily for its large nut size and
high yield capacity. It forms a vigorous tree
with an open crown. Ennis is late coming into
leaf. There are usually just one or two nuts per
cluster. The husk tends to clasp the nut and
many nuts fall in the husk. It is susceptible to
bacterial blight and moderately susceptible to
big bud mites. Pollen is shed mid-season,
female flowering is mid to late. Many flowers
are borne on the catkin peduncles (stalks).
Suitable pollinisers are Merveille de Bollwiller
(in cooler areas only), Alexandra, and Keen’s
Late.
Ennis is very productive with large attractive
nuts yielding 43 – 46% kernel. The shell is
pale, glossy, striped, and easily cracked.
Kernels are usually free of fibre and do not
blanch.
When grown in well managed orchards on
high quality soils in areas with high sunshine
hours, the kernels are generally plump;
however shrivelled kernels and blank nuts
(nuts with no kernels or small undeveloped
kernels) are common when Ennis is grown in
less than ideal environments.
Fig.5: Ennis variety –
in-shell, unblanched kernel, blanched kernel
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 4 of 9
Tonda di Giffoni
Tonda di Giffoni is an Italian variety of ancient
origin, grown in the province of Salerno (near
Naples). The tree is vigorous and semi-erect.
It holds its leaves late into the autumn and the
new leaves emerge very early (mid-August in
the Bay of Plenty). The husk is slightly longer
than the nut; many nuts fall in the husk.
Tonda di Giffoni is resistant to bacterial blight,
and only slightly susceptible to big bud mites.
Female flowering and pollen shed are mid-
season. Suitable pollinisers are Barcelona,
Butler, and Lansing.
Tonda di Giffoni is very precocious and
productive. The medium-sized nuts are round,
brown with a distinct stripe and very
pronounced grooves on the sides yielding 44 -
47% kernel. The kernels are round, often
grooved, and may have light fibre. They
blanch very well.
Tonda di Giffoni has yielded well in most parts
of New Zealand but has problems with high
levels of mould in most orchards. It is
sensitive to frosts in spring. It has relatively
low chill requirements for catkins and
vegetative buds and may be suited to areas
with mild winters in the drier areas of New
Zealand.
Fig.6: Tonda di Giffoni variety –
in-shell, unblanched kernel, blanched kernel
Tonda Romana
Tonda Romana is an Italian variety of ancient
origin, and is the main variety in the hazelnut
orchards of Viterbo province (north of Rome).
The tree is of moderate to low vigour, semi-
erect in form, and has many suckers. The
husk is slightly longer than the nut; most nuts
fall free of the husk.
Tonda Romana is resistant to big bud mites
but is rather susceptible to bacterial blight.
Pollen shed and female flowering are mid-
season. Suitable pollinisers are Lansing,
Tonda di Giffoni, and Merveille de Bollwiller.
Tonda Romana has moderate to high yields.
The nut is medium to small in size, round, with
a dull light brown shell yielding 44-48% kernel.
Kernels are round, usually free of fibre and do
not blanch. Black tips can be a problem due to
splitting along the shell suture
Fig.7: Tonda Romana variety –
in-shell, unblanched kernel, blanched kernel
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 5 of 9
Whiteheart
Whiteheart is the main variety grown
commercially in New Zealand. It is a New
Zealand variety selected in the 1980s from a
number of plantings of a variety sold as
“Waterloo” by Duncan and Davies.
The tree has low vigour, an erect form, and
suckers strongly. The husk is nearly twice as
long as the nut and clasps the nut tightly.
Many nuts fall in the husk. Clusters often have
3 to 8 nuts per cluster. Some clusters tend to
hang in the trees into winter.
Whiteheart is susceptible to bacterial blight
and big bud mites. Pollen is shed mid-season
but female flowering is very late.
Whiteheart has moderate to high yields when
grown in well-managed orchards. The
medium-sized, round nut has a shiny brown,
thin shell yielding 47 to 50% kernel. Kernels
are round, free of fibre, and blanch very well.
Whiteheart is the main variety grown in
commercial orchards in New Zealand because
good nut quality can be achieved in all growing
regions. Whiteheart is a low vigour variety and
orchards need to be planted with closer tree
spacing than is common with more vigorous
varieties. Good orchard management is
essential to achieve acceptable commercial
yields.
Fig.8: Whiteheart variety –
in-shell, unblanched kernel, blanched kernel
Varieties used as pollinisers
Alexandra
Alexandra is a New Zealand selection from
Alexandra in Central Otago. It forms a large,
vigorous, open, spreading tree with few
suckers. The husk is about the same length
as the nut and most nuts fall free of the husk.
It is moderately resistant to big bud mites and
is susceptible to bacterial blight. It sheds
pollen over a long period late in the winter.
Female flowering and bud burst are very late.
If other late pollinisers are present, Alexandra
has heavy yields of nuts. The nuts are
flattened, blocky in shape, with a dull pale
cream/brown colour drying to a dull
grey/brown. Nuts have very thick shells, with
small elongated kernels with a moderate to
light fibre cover.
Alexandra is the main late polliniser used for
late flowering cultivars such as Whiteheart and
Ennis. It has large numbers of catkins, often in
large “bunches” of more than 10 catkins.
Fig.9: Alexandra variety –
in-shell, unblanched kernel, blanched kernel
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 6 of 9
Butler
Butler originated as a seedling in Oregon, USA
and was introduced into cultivation in 1957. It
appears to be a cross between Barcelona and
Daviana. It is very vigorous with an erect tree
form. The husk is slightly shorter than the nut
and most nuts fall free of the husk. Nut drop
occurs over a long period.
It is susceptible to bacterial blight and big bud
mites. It drops pollen for a long period early in
the season but the female flowers are late.
Suitable pollinisers are Merveille de Bollwiller
(in cooler regions), Alexandra, and Keen’s
Late.
Butler is very productive and has yielded well
in most parts of New Zealand. Nuts have a
high percent kernel (47 – 49%). The kernels
do not blanch and are sometimes considered
to have a bland flavour. Shrivelled kernels are
common.
Fig.10: Butler variety –
in-shell, unblanched kernel, blanched kernel
Keen’s Late
Keen’s Late is a New Zealand selection
chosen for its late pollen production. It forms
an erect tree of moderate vigour. The husk
encloses the nut tightly and many nuts fall in
the husk.
It is susceptible to bacterial blight and
moderately susceptible to big bud mites.
Pollen shed is very late, extending well into
early September. Female flowers emerge
before, or about the same time, as catkin
extension. Suitable pollinisers are Merveille de
Bollwiller and Alexandra.
Keen’s Late crops well, yielding elongated
nuts with 26 – 30% kernel. Kernels do not
blanch.
Fig 11: Keen’s Late variety –
in-shell, unblanched kernel, blanched kernel
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 7 of 9
Kentish Cob
Also called Du Chilly or Longue d’Espagne,
Kentish Cob originated as a seedling selection
in Kent, England.
The tree is of relatively low vigour, semi-erect
and productive. It is late coming into leaf. The
husks extend beyond the nut, 50 to 60 % of
the nuts fall free. It is moderately resistant to
big bud mites and susceptible to bacterial
blight. Pollen shed is late, making it a useful
late polliniser. Female flowering is late.
Suitable pollinisers are Merveille de Bollwiller
and Alexandra.
The nuts are large, long, and flattened. The
shell is thin (48% kernel) and the nuts are
easily cracked. The kernels are long, free of
fibre, sweet and do not blanch
Fig.12: Kentish Cob variety –
in-shell, unblanched kernel, blanched kernel
Lansing
Lansing originated in Oregon, USA. The tree is
semi-erect and vigorous. Leaves fall late but
bud burst is early. Husks are the same length
as the nut and most nuts fall free of the husk.
Lansing is resistant to bacterial blight and big
bud mites. Pollen shed and female flowering
are mid-season. Suitable pollinisers are Tonda
di Giffoni and Merveille de Bollwiller.
Lansing is productive, with large attractive
round nuts, brown with a distinct stripe. The
shell is thinand easily cracked, yielding 44 –
50% kernel. The large round kernels are
usually free of adhering fibre but are
susceptible to mould and shrivelling.
Lansing is a very productive, healthy variety
that is a valuable mid-season polliniser. The
nut is a similar size to Ennis but darker brown
and globular to oblate in shape rather than
ovoid.
Fig.13: Lansing variety –
in-shell, unblanched kernel, blanched kernel
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 8 of 9
Merveille de Bollwiller
Merveille de Bollwiller is called Hall’s Giant in
Australia and the USA. The tree is vigorous
and spreading with dark green leaves.
Merveille de Bollwiller is late coming into leaf.
It has distinctive dark red to purple buds.
Catkins have a purple blush. The husk is
slightly longer than nut but most nuts fall free
of the husk.
Merveille de Bollwiller is resistant to bacterial
blight and big bud mites. Pollen is shed late,
often for a short period. Female flowering is
late. Suitable pollinisers are Alexandra and
Keen’s Late.
Merveille de Bollwiller has low yields of
attractive medium to large nuts yielding 36 –
41% kernel. The shell is thick, brown and
glossy. The kernel is round to oval, firm and
free of fibre. It blanches well.
Fig.14: Merveille de Bolwiller variety –
in-shell, unblanched kernel, blanched kernel
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 2: Hazelnut Varieties Page 9 of 9
PRODUCTION CHARACTERISTICS OF FIVE HAZELNUT VARIETIES WITH POTENTIAL FOR
COMMERCIAL PRODUCTION IN NEW ZEALAND
Variety Potential
Use
Kernel % Advantages Disadvantages
Barcelona Kernel
In-shell
39-43% High yielding vigorous tree.
Nut can be used for in-shell or
roasted kernel markets.
Not susceptible to big bud mite.
Susceptible to “brown-stain”.
Heavy fibre on the kernel in
damper climates.
Ennis In-shell 43-46% High yielding.
Medium vigour tree.
Very large, attractive nut.
Susceptible to bacterial blight.
Requires ideal growing
conditions to produce good
quality nuts.
Tonda di
Giffoni
Kernel 44-47% Good kernel flavour.
Kernels blanch well.
High yielding vigorous tree.
Susceptible to mould on the
kernels.
Tonda
Romana
Kernel 44-48% Excellent kernel flavour.
Medium vigour growth habit. Not
susceptible to big bud mite.
Kernels do not blanch.
Susceptible to bacterial blight.
Numerous suckers.
Whiteheart
Kernel 47-50% Good kernel flavour.
Kernels blanch well.
Low vigour growth habit.
Produces high quality nuts in
most regions.
Numerous suckers.
Many nuts retained in husk.
Some nut clusters do not fall
at harvest.
Susceptible to big bud mite
and bacterial blight.
Further information:
Only the main commercial varieties and their pollinisers are described in this bulletin. For detailed
descriptions and illustrations of all varieties available in New Zealand, see www.hazelnut.org.nz.
Baldwin, B. 2010. Hazelnuts: Variety assessment for south-eastern Australia. RIRDC publ. No.
09/178. Available at https://rirdc.infoservices.com.au/items/09-178
The “Guidelines for Growing Hazelnuts in New Zealand” bulletins were produced by the Hazelnut
Growers Association of NZ with financial assistance from the Ministry for Primary Industries
Sustainable Farming Fund and the NZ Tree Crops Association.
Murray Redpath is Chairman of the Hazelnut Growers Association of NZ.
All photographs: Murray Redpath
Disclaimer
While the author has taken all reasonable skill and care in assessing the accuracy of the information in this report, none of the
organisations involved accepts any liability, whether direct, indirect or consequential, arising out of the provision of information
within this report.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Flowering and pollination Page 1 of 5
Guidelines for Growing Hazelnuts in New Zealand
Bulletin 3: Flowering and pollination
Murray Redpath. May 2016
Hazels are monoecious (i.e. they have separate
male and female flowers on the same tree) and
are wind pollinated. The pollen from the catkins
(Fig. 1) is released on warm dry days in winter
and drifts through the orchard onto the emerged
stigmas of the female flowers (Figs. 2 to 4).
Fig. 1:Hazel catkins showing the sequence from just
starting to elongate (left), fully elongated with
maximum pollen shedding (middle), and completed
(right).
Most pollen is released during warm sunny
days, when gentle breezes are more likely. Wind
can carry pollen grains great distances, but nut
set decreases when the distance from the
pollinisers exceeds 15 metres. Orchard layouts
should be designed so that all trees are no
further than 15 – 20 metres from a polliniser.
This means that pollinisers should make up 8 to
10%of the orchard. Typical systems for
distributing pollinisers in the orchard are
discussed in Bulletin 2 Orchard Development.
Hazels are self-incompatible, which means that
a tree will not set nuts with its own pollen or
pollen from another tree of the same variety.
Some combinations of hazel varieties are also
cross-incompatible.
Compatibility is controlled by a single gene.
Hazels have 2 sets of chromosomes so each
variety has 2 alleles (known as the “S” alleles)
associated with pollen. Both are expressed in
the female flowers but pollen may express one
or both alleles. If an allele expressed in the
pollen matches either of the alleles in the female
flower, then the cross will be incompatible.
Hazel flowering biology
Catkins begin to form early in the summer and
are visible by mid-December. Varieties that shed
pollen early begin to differentiate earlier than
those shedding later. Catkins grow to full size
over about 3 months. The pollen cells then
continue to develop and mature within the
catkins. Catkins will not elongate until the pollen
inside is fully mature, which depends on the
accumulation of a critical amount of chilling.
Once the catkins have received enough chilling,
they elongate in response to warmth and the
pollen is released. The period of pollen release
varies from variety to variety. Butler and
Alexandra often release pollen over a 4 to 6
week period whereas Merveille de Bollwiller
often has a compressed pollen release of only 2
to 3 weeks. With each warm day, catkins
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Flowering and pollination Page 2 of 5
continue to elongate and release pollen until
they are fully elongated and turn brown.
The female flowers are borne within the
overlapping scales of compound buds. These
buds are very difficult to distinguish from
vegetative buds until flowering occurs. Each
flower consists of a pair of stigmatic styles that
emerge from the top of the bud during flowering
and gradually elongate. These are the little
“whiskers”, usually red in colour, that emerge
from the end of the bud.
Fig. 2: Flowers at the “red dot” stage (left) with
stigmatic styles extended less than 1 mm.
Fig. 3: Butler flowers with extended stigmatic styles.
Fig. 4: Stigmatic styles shrivelling after pollination
Most of the surface of the style is receptive so
they are able to be pollinated from the time they
first emerge (Fig. 2) until the total length of the
style has emerged. If not pollinated, these
stigmatic styles can remain receptive for two to
three months. If the exposed surfaces are
damaged (e.g. by frost), the lower parts that are
still protected by the bud scales will emerge with
functional receptive surfaces. So pollen at the
start of the main flowering period is less
important than having plenty of pollen over the
middle and later part of the flowering period.
When the flowers have been pollinated, the
stigmas darken and shrivel (Fig. 4)
Climatic factors affecting hazel pollination
Like most deciduous trees, hazels enter
dormancy in response to shortening day length.
A period of chilling(at temperatures between
0°Cand 7°C) is required before warm weather
can break the bud dormancy. Catkins, female
flowers, and leaf buds have different chilling
requirements. As a general rule, female flowers
have greater chilling requirements than catkins.
Once this chilling requirement has been
reached, a certain number of warm days are
required before the catkins open and release
pollen.
Most varieties are protandrous, i.e. pollen is
released before female flowering occurs. This is
to be expected when chill requirements for
catkins are lower than for female flowers. Some
varieties are frequently homogamous (pollen
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Flowering and pollination Page 3 of 5
shed and female flowering occur
simultaneously). Tonda di Giffoni is often
homogamous at Wairata in the Bay of Plenty
(see Fig. 5). Protogyny, where female flowering
occurs prior to pollen shed, is usual in a few
varieties (e.g. Keen’s Late) but also occurs more
commonly in other varieties in climates with
severe winters. The limited information available
from Central Otago indicates that more hazel
varieties may be homogamous and protogynous
there in colder winters, with pollen release from
all varieties occurring during August.
The chill requirements of each variety are
genetically controlled so the order in which
varieties commence shedding pollen or
flowering will usually be similar between
seasons and locations. For example, Butler
(catkin chill requirements of 100-170 hours) will
usually drop pollen before Merveille de Bollwiller
(catkin chill requirements of 290-365 hours). The
sequence of pollen release for varieties grown in
New Zealand is illustrated in Fig. 5.
In general, pollen is shed earlier in locations with
warmer winters, and for each location is also
shed earlier in warmer seasons (provided the
minimum chill requirements are met). This
causes differences in the overlap of pollen
release with female flowering between different
climatic zones. For example, the varieties
commonly recommended as pollinisers for the
Whiteheart variety are Merveille de Bollwiller
and Alexandra. This was based on early
research done in Canterbury. Later research
showed that Merveille de Bollwiller usually
sheds most of its pollen before the main
Whiteheart flowering in the warmer regions from
Nelson north, and Alexandra frequently only
covers the early Whiteheart flowers. In these
regions a variety that releases pollen later is
required to ensure complete coverage of the
Whiteheart flowering period.
Fig. 5: Date of pollen release and female flowering for hazel varieties at Wairata, Bay of Plenty 2004-2013.
Butler
Barcelona
Lansing
Ennis
Tonda di Giffoni
Tonda Romana
Whiteheart
Alexandra
Merveille de Bollwiller
Kentish Cob
Keen's Late
Key
Pollen release
Female flowering
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Flowering and pollination Page 4 of 5
Selecting the correct pollinisers
Hazelnut orchards depend on specific pollinisers
to successfully pollinate each commercial
variety. These pollinisers must have pollen that
is compatible with the flowers of the commercial
variety and this pollen must be shed during the
main flowering period each year. An ideal
polliniser is one that sheds compatible pollen at,
or immediately following, the peak of female
flowering of the main crop cultivar. Because the
timing of pollen shed and stigma emergence on
the female flowers are controlled by
temperature, it is recommended that at least
two, and ideally three, pollinating varieties are
used to allow for seasonal variations in the time
of pollen shedding.
Overseas research has shown that some
varieties (e.g. Tonda Romana) have a high
proportion on nonviable pollen in the catkins.
These varieties should not be used as
pollinisers.
Varieties that are potential pollinisers for
commercial varieties should be tested for
compatibility with other varieties before being
recommended. Table 1 provides a guide to the
compatibility of varieties grown in New Zealand.
If the timing of pollen release coincides with
female flowering of the selected female parent
(based on research in New Zealand) an
indication is given whether the variety is suited
as an early, mid-season or late polliniser.
Ale
xandra
Barc
elo
na
Butler
Ennis
Keen's
Late
Kentish C
ob
Lansin
g
M.d
e B
ollw
iller
T.d
i G
iffo
ni
Tonda R
om
ana
Whiteheart
? 1 3 1 ? 8 14 3 5 15 2 10 20 10
Barcelona 1 2 ?L +E + +L +E +L +M +M
Butler 2 3 +E,M + +E +L +E +E +
Ennis 1 11 ?M + +L +E + +E + + +
Keen's Late ? ? ? ? + + ? + +E ? ? ?
Kentish Cob 8 14 ?E,M + + + ? + +E + + +
Lansing 1 3 ?M,L + M +M +E +E +E
Merveille de Bollwiller 5 15 +M + + +E +L +E + + + +
Tonda di Giffoni 2 23 ? +E +E +M,L ? + +E,M,L + +M,L +L
T.G.D.L. 2 7 ? + + + ? + + + + +
Tonda Romana 10 20 ? + + +E,M ? +L +E +L +E
Whiteheart 2 10 +M + + + +L +E +E +E
+ indicates that pollen is compatible with the flower of the female tree.
A blank cell indicates an incompatible cross
? A "?" indicates that the compatibility is unknown
Text indicates whether pollen of the male parent is shed early (E), mid-flowering (M) or late (L) in the flowering period of the selected female parent.
Variations may occur in other parts of New Zealand.
Dates have been calculated from records taken at Wairata Forest Farm, Bay of Plenty.
Table 1. Pollen-flower compatibility of hazelnut varieties grown in New Zealand.
Prepared for Ministry for Primary Industries Sustainable Farming Fund Project L08-088 by M. Redpath. Revised 2016.
Alleles
Expressed
Pollinisers
Female parent
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Flowering and pollination Page 5 of 5
Table 2. Recommended pollinisers for the main commercial varieties grown in New Zealand
“Warmer regions” include Nelson and most of the North Island; “Colder regions” includes most of the South Island except Nelson. Accurate recommendations are not currently possible for Central Otago due to a lack of data from that region. Variety Warmer regions Colder regions Barcelona 25% Lansing
75% Merveille de Bollwiller 25% Lansing 75% Merveille de Bollwiller
Ennis 25% Merveille de Bollwiller 25% Alexandra 50% Keen’s Late
25% Merveille de Bollwiller 50% Alexandra 25% Keen’s Late
Tonda di Giffoni 25% Barcelona 50% Lansing
25% Barcelona 50% Lansing 25% Merveille de Bollwiller
Tonda Romana 50% Lansing 50% Merveille de Bollwiller
50% Lansing 50% Merveille de Bollwiller
Whiteheart 25% Alexandra 75% Keen’s Late
25% Merveille de Bollwiller 50% Alexandra 25% Keen’s Late
The “Guidelines for Growing Hazelnuts in New Zealand” bulletins were produced by the Hazelnut Growers Association of NZ with financial assistance from the Ministry for Primary Industries Sustainable Farming Fund and the NZ Tree Crops Association. Murray Redpath is Chairman of the Hazelnut Growers Association of NZ. All photographs: Murray Redpath Disclaimer While the author has taken all reasonable skill and care in assessing the accuracy of the information in this report, none of the organisations involved accepts any liability, whether direct, indirect or consequential, arising out of the provision of information within this report.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 1 of 9
Guidelines for Growing Hazelnuts in New Zealand
Bulletin 4: Nut Development and Quality
Murray Redpath. May 2016
Successful hazelnut production depends on
producing high yields of nuts that meet the
quality standards imposed by the market. An
understanding of the stages in the development
of the hazel nut can help growers understand
the causes of many of the nut quality and
production problems.
Nut development
Nut development starts with pollination of female
flowers over winter. Hazelnut female flowers
consist of pairs of stigmatic styles, usually red in
colour, that emerge from the bud scales. Each
flowering bud can contain between 4 and 16
individual flowers, each with the potential to
grow into a nut if pollinated. Unlike most
flowering plants, hazelnut flowers do not have
an ovary and mature egg cells ready for
fertilisation at flowering. Instead there is a tiny bit
of tissue, called an ovarian meristem, at the
base of the stigmatic styles. If pollination with
compatible pollen occurs, pollen tubes grow
down to the base of the styles and enter a
resting period.
Successful pollination stimulates the ovary to
start developing from the ovarian meristem.
After nearly four months of slow growth, the
ovary grows rapidly within a developing shell
and husk over 5 to 6 weeks. During this period
the ovaries mature, the resting sperm becomes
activated and fertilisation takes place. In New
Zealand this is probably during late November
and December in most regions. The shells are
full size by mid to late December.
Kernels grow rapidly after fertilisation, taking
about 6 weeks to reach full size. A further 6 to 8
weeks later, the nuts reach full maturity. At this
point they can be easily dislodged from the
husk.
The period from fertilisation to nut maturity is a
critical time for nut quality. Anything that slows
or stops the progress of the rapidly developing
nut will have an impact on the quality of that nut.
Pollination
Ovule development
Fertilisation
Shell development
Kernel development
Harvest
Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Fig. 1: Stages of nut development.
(The exact timing will vary with variety and location. Early flowering varieties develop earlier. Cooler southern regions
may be four to six weeks later than northern locations.)
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 2 of 9
Quality
International quality standards
A number of quality standards exist for both in-
shell hazelnuts and hazelnut kernels. Some
producing countries and regions, such as Turkey
and Oregon (USA) have quality standards for
hazelnuts sold by their industries, and some
countries have minimum standards for the
importation of hazelnuts (e.g. USA).
International standards have been set by the
United Nations Economic Commission for
Europe (UNECE, 2007 & 2010) and the OECD
(OECD 2011). These standards are all similar.
The OECD standard is the most recent and is
likely to be the standard that New Zealand
growers or processors will have to meet for
exported nuts and kernels. The OECD
standards, which include photographs illustrating
faults and minimum requirements for these
faults can be downloaded from
http://www.oecd.org/tad/code/50300442.pdf.
These standards grade in-shell nuts and kernels
into three grades, depending on the number of
defects. These grades are: Extra Class, Class I
and Class II, in order of increasing incidence of
defects. Class II can be taken as the minimum
quality required for exported nuts to meet
international standards.
In-shell nuts
In-shell nuts must have intact, clean shells free
from stains or blemishes affecting more than
25% of the shell surface. The kernels must be
sufficiently developed (filling at least 50% of the
shell cavity), not shrivelled, and free from mould
or damage by pests. In-shell nuts should have a
moisture content of less than 12% for the whole
nut or 7% for the kernel. Most of the nuts (at
least 90%) must be of the specified variety.
The OECD Class II standard allows a maximum
of 20% defective in-shell hazelnuts for shell or
kernel defects, with a maximum of 12% blanks
or poorly filled, and 6% rancid, mouldy, rotting,
or damaged by pests.
Large nuts are preferred by markets for in-shell
nuts. Minimum size under the OECD standard is
12 mm in diameter. The standards adopted by
the Hazelnut Growers of Australia (HGA) are
typical of the size grades used by in-shell
markets:
Small: up to 13 mm
Medium: 13.01 to 18 mm
Large: 18.01 to 19.5 mm
Very Large: 19.51 to 22 mm
Jumbo: over 22 mm
The HGA standards do not allow mould or insect
damage, allow just 5% blank nuts and specify a
maximum 5% kernel moisture content.
Kernels
OECD requirements for hazelnut kernels are
similar to those stated for the kernels of in-shell
hazelnuts with additional provisions for the
intactness of the kernel (loss of parts of the
pellicle or kernel more than 3 mm in diameter
and 1.5 mm in depth during cracking) and a
lower moisture content requirement of no more
than 6% moisture.
OECD Class II allows a maximum of 18%
defective hazelnut kernels, of which no more
than 8% are insufficiently developed (including
shrivelled or shrunken), 2.5% mouldy, and 6%
rancid, rotten, have an off odour or flavour, or
are insect damaged. Maximum tolerance for
damaged kernels and pieces greater than 5 mm
is 10%; and 2% for pieces smaller than 5 mm.
Not more than 8% can be twin kernels, or 10%
kernels of varieties other than that specified.
These standards apply to nuts at the export or
market control stage after preparation and
packing. For growers, achieving acceptable nut
quality at harvest depends on the ability of the
post-harvest cleaning and processing systems
to remove defective nuts. Blanks and poorly
filled nuts, including badly shrivelled kernels, can
be separated during cleaning or after drying,
using air leg systems. Kernel defects are hidden
until cracking so nuts for the in-shell trade need
to have very few kernel defects.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 3 of 9
For nuts that are cracked, defective kernels
require removal by hand and a high incidence of
defective kernels results in the processing line
slowing or extra labour being required. These
extra costs are likely to be passed on to the
grower, or crops may be rejected.
Nut quality defects and factors
influencing nut quality
Defective nuts include blanks (nuts with no or
very small kernels within the shell), twins (two
kernels in a shell), mouldy nuts, kernels with
black tips (caused by a weak shell suture),
poorly filled nuts, and shrivelled kernels.
The percentage of defective nuts is influenced
by both genetics (some varieties are more
susceptible to defects) and environmental
conditions that promote expression of those
defects. There are important varietal differences
in the production of blanks and twins, and in
susceptibility to mould.
The significance of nut quality defects depends
on whether defective nuts can be effectively and
economically removed from the crop before
sale. Blanks and poorly filled nuts, plus nuts with
very shrivelled kernels, can be separated
mechanically from the well filled nuts during the
cleaning or drying processes, usually using air
leg systems after drying and sizing. Shell
defects are removed by hand on sorting tables.
Kernel defects are also removed by hand after
cracking as they pass over sorting tables.
Automated laser sorters that blow out shell and
defects from cracked nuts are now available
overseas.
Common nut quality problems
Blank nuts
Blanks are nuts where the shell is empty or has
an undeveloped kernel filling less than 25% of
the shell.
Blanks occur when pollination stimulates the
shell to develop but the kernel fails to develop
normally. Either fertilisation fails to occur or
embryo development is stopped at an early
stage, leaving a small undeveloped kernel. This
may be caused by any of the main factors that
place the tree under stress – low soil fertility,
poor tree nutrition, adverse climatic conditions
(such as drought or intense heat), lack of light in
the canopy, or heavy crop load. Some varieties,
such as Barcelona and Tonda Romana, produce
more blanks than others. Cool temperatures
during the time of fertilisation( Late November –
December in NZ) have been suggested as one
possible cause of blanks.
Blanks are not a problem when cracking for the
kernel market but are unacceptable in nuts sold
in-shell.
‘Brown Stain’
Brown stain is a disorder that causes distorted
shells and leads to an increase in the incidence
of blanks and poorly filled nuts. The name for
the disorder describes the symptoms: brown
liquid oozes from the shell of affected nuts in
late December/ early January, staining the
surface of the nut. The cause is unknown but it
is suspected to be a physiological problem.
In severe cases the shell is distorted and the
kernel destroyed. In less severe cases, the
brown stained area of the shell has a pale, dull,
sunken appearance. The shell is often softer in
the affected area (Fig. 2).
Fig. 2: Barcelona nuts with shells distorted by
Brownstain.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 4 of 9
Shell defects
Shell defects are relevant only for nuts destined
for the in-shell markets. These defects include
damage by insects, scarring by bacterial blight,
mould or stains making up more than 25% of the
shell surface. The shell should be free of any
soil residues or adhering husk. Nuts with shell
defects are usually removed by hand after
drying.
Insect damage to the shell surface is not
common in New Zealand but caterpillars
(species not identified) have been observed
feeding between the husk and nut surface on
developing nuts, causing distortion of the
developing shell or marking of the shell surface.
Superficial shell cracks
Nuts of the Butler variety have a high incidence
of superficial marks that form long pitted areas
on the shell resembling short cracks but the
marks do not penetrate through the shell (Fig.
3). The cause of these is unknown but they can
affect a significant proportion of the nuts. The
marks darken and become mouldy more rapidly
than the rest of the shell surface.
Fig. 3: Superficial cracks on Butler nuts
Shell colour
Some nuts have a shell colour that is darker
than normal, usually a greyish brown colour.
These nuts are often empty or poorly filled. Very
dark or black nuts are usually nuts from the
previous season.
Shell stains
Localised discoloration of the shell is classed as
a defect if it covers more than 25% of the
surface area of the shell. It can be caused by
sun scorch on short husked varieties like Ennis.
Blight scars
Bacterial blight can develop on the husks and
infect the surface of the soft developing shell,
resulting on slightly sunken greyish or dark
brown lesions (Fig. 4). It is most common on
varieties susceptible to bacterial blight such as
Ennis and Barcelona. Blight scars are usually
too small to be considered a defect under OECD
standards.
Fig. 4: Scars caused by bacterial blight(Xanthomonas
campestris pv. corylina)
Split sutures
Some varieties have weak sutures and hairline
cracks develop along the sutures of some nuts
(Fig. 5). When these split, the tips of the kernels
can blacken and frequently become mouldy.
Split sutures are common in Barcelona and
Tonda di Giffoni.
Fig. 5: Barcelona nuts with split sutures
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 5 of 9
External mould
Mould develops on the shell when nuts are left
in damp conditions for too long after nut fall. This
can occur while the nuts are on the ground or
after harvest if they are not washed and dried
immediately. It often starts on the apex of the
nut, especially on those varieties with a downy
shell surface such as Barcelona.
Fig. 6: External mould on Ennis hazelnuts.
Soil, silt or clay on the shell surface
Any soil or foreign material on the surface of the
shell is a possible source of contamination. All
nuts should be washed and the shell surface
sterilised before drying.
Fig. 7: Fine silt contaminating the lower shell
Kernel Defects
Poorly filled nuts, shrunken and shrivelled
kernels
Poorly filled nuts have kernels that fill more than
25% but less than 50% of the shell cavity.
Shrunken nuts have sunken areas in the kernel.
This has been attributed to rapid kernel growth
in extremely high temperatures. Shrivelled
kernels have wrinkling over more than 50% of
the surface of the kernel.
Anyenvironmentalfactorthatstressesthetreesduri
ngkerneldevelopment(January – February)
increases the number of empty, poorly filled,
shrunken and shrivelled nuts. These factors
include low soil fertility, poor tree nutrition,
adverse climatic conditions (such as drought or
intense heat), lack of light in the canopy, or
heavy crop load. The proportion of poorly filled
and shrivelled kernels is higher in varieties with
large nuts such as Ennis than in varieties with
smaller nuts such as Whiteheart. Bacterial blight
has also been implicated in the incidence of
shrivelled kernels. Blight scars can partially
girdle the shoot supporting the nut cluster,
disrupting the flow of photosynthates to the
developing nuts.
Kernels with minor shrivelling or poor fill can be
used for paste or oil provided the flesh is not
tough and leathery.
Fig. 8: Poorly filled nuts
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 6 of 9
Fig. 9: Shrivelled kernels. The kernels above the line
are suitable for paste or oil; those below the line are
too shrivelled.
Twin kernels
Twin kernels are considered defects because
the resulting individual kernels are usually below
the minimum size for most kernel grades. Mould
can sometimes develop in the gap between the
two kernels.
Fig. 10: Twin kernels (Barcelona)
Mould
Any visible growth of mould either on the outside
or inside of the kernel is considered a defect
(Fig. 11). Internal mould (on the surface of the
internal cavity of the kernel) can only be
detected by splitting the kernel. Mould is often
associated with severely shrivelled kernels and
the fungi may be secondary opportunists
invading stressed kernels.
Fungal species associated with mould on
hazelnuts include Aspergillus spp, Penicillium
spp, Cladosporium spp, and Phomopsis spp.
Overseas research has found that spores may
be present throughout nut development but will
not necessarily develop in the nut. Aspergillus
flavus and Aspergillus parasiticusare known to
produce aflatoxins and nuts contaminated with
these moulds are unsuitable for human
consumption.
The main influences on the incidence of mould
are variety and climate, with significant
differences in susceptibility of varieties to mould.
Tonda di Giffoni frequently has mouldy kernels;
Whiteheart seldom has problems with mould.
Mould is highest after wet weather in the spring
or during harvest. Warm humid conditions favour
the growth of these moulds and growers need to
ensure that nuts are not kept in damp conditions
during the harvest and post-harvest period.
Control of mould through orchard management
is difficult. Experiments using fungicide sprays in
the spring, autumn and winter failed to reduce
the incidence of mould in Oregon. Pruning to
keep the canopy open may help to minimise
mould development.
Black tips
Black tips are caused by necrosis of the kernel
tip, sometimes with visible mould (Fig. 11). The
necrosis extends a few millimetres into the
kernel. Black tips are most common in varieties
with weak sutures. Shells crack along the
suture, allowing the entry of moisture and fungal
spores.
Black tips are listed as kernel defects in cultivar
trials but are not defined as a distinct class of
defect in any of the international standards. The
only OECD defect definition that would cover
black tips is „kernel discoloration‟.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 7 of 9
Fig. 11: Kernels affected by visible mould (top) and
black tips (bottom two rows)
Kernel discoloration
The OECD standard states that kernels must be
“free from blemishes, areas of discoloration or
spread stains in pronounced contrast with the
rest of the kernel affecting in aggregate more
than 25% of the surface of the kernel”. This is
further defined as “apparent localized alterations
of external or internal colour from any cause
whatsoever…but excluding blemishes caused
by a more serious defect such as mould, decay
or damage by pests” (OECD, 2011). Any colour
blemish that does not affect the edibility of the
kernel is not classed as a defect. A taste test is
recommended to decide whether or not edibility
is affected.
Internal deterioration and rancid nuts
Some kernels deteriorate internally with no
significant change to the appearance of the
pellicle. The pellicle sometimes darkens and lifts
from kernel beneath. This deterioration turns
the kernel rancid; the colour of the kernel flesh
turns yellow and waxy in appearance (Fig.12).
This damage is often only evident after
blanching and the frequency of this defect can
only be determined by cutting a sample of
kernels to check the kernel interior.
Fig. 12: Kernels showing internal deterioration.
Some of this damage was not evident until the nuts
were blanched.
Fibre
The absence of fibre on the kernel is desirable
for nuts destined for the in-shell trade or kernels
to be sold for use as raw kernels. The fibre gives
a bitter taste to the kernel and detracts from the
general appearance of the raw kernels. Fibre is
not a concern for blanched or roasted nuts
provided it can be completely removed with the
pellicle. For varieties that do blanch well (e.g.
Campanica, Nocchione), blanching of the kernel
by lightly roasting nuts destined for the in-shell
trade causes the fibre to fall away with the
pellicle when the nuts are cracked.
Corky fibre acts as a sponge, holding moisture
around the kernel and slowing the drying of the
kernel. It can also impede the separation of the
shell from the kernel after cracking if the fibre is
adhering tightly to both the pellicle and the inner
surface of the shell (Fig. 13).
Fig. 13: Shell adhering to fibre on a Barcelona nut
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 8 of 9
Insect damage
Hazelnut kernels can be damaged by green
shield beetles (Nezara viridula). These feed on
both developing and mature kernels. Damage
depends on the time of attack. If the shell is still
soft and the kernel is still developing, the kernel
can be deformed and/or brown spots appear on
the surface of the kernel. The kernel develops a
disagreeable taste. If the attack occurs after the
shell has hardened and the kernel is fully
developed, then the damage may be limited to
the development of white spots, sometimes with
a pinhead sized black spot in the centre. These
white areas darken when kernels are roasted.
Damaged kernels become rancid more easily
than normal kernels.
The damage is difficult to detect on raw kernels,
especially those with a covering of fibre, unless
the nut has become distorted or developed
mould on the damaged site. Insect damage
becomes evident once the kernels are blanched.
OECD standards allow this sort of damage as
long as the kernel flesh is not affected and the
spot does not exceed 3 mm in diameter and
3 mm in depth.
Fig. 13: Damage caused by the green vegetable bug
Nezara viridula
Further reading
OECD. 2011. International Standards for Fruit and Vegetables: In shell Hazelnuts and Hazelnut Kernels.
International Standards for Fruit and Vegetables, OECD Publishing.
http://dx.doi.org/10.1787/9789264166721-en-fr
Redpath, M.S. 2013. Assessing regional nut quality differences in New Zealand hazelnut varieties. MPI
Sustainable Farming Fund report L12-111. 49 p
The “Guidelines for Growing Hazelnuts in New Zealand” bulletins were produced by the Hazelnut
Growers Association of NZ with financial assistance from the Ministry for Primary Industries Sustainable
Farming Fund and the NZ Tree Crops Association.
Murray Redpath is Chairman of the Hazelnut Growers Association of NZ.
All photographs: Murray Redpath
Disclaimer
While the author has taken all reasonable skill and care in assessing the accuracy of the information in this report, none of the
organisations involved accepts any liability, whether direct, indirect or consequential, arising out of the provision of information within
this report.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 6: Nut Development and Quality Page 9 of 9
How to minimise nut quality problems in your hazelnut crop
Variety selection
Choose varieties that are adapted to your local climatic and soil conditions
High yielding varieties with large nuts (Ennis, Butler, Lansing, Barcelona) require high quality soils
(Class 1 or 2), excellent shelter, and ideal climatic conditions (adequate soil moisture, high sunshine
hours, temperatures of 20 - 35˚C from late November to harvest)
Varieties that are susceptible to black tip and mould (Lansing, most of the Italian varieties) require dry
weather over late summer and harvest.
Growers in locations with cool, damp climates should plant varieties with small to medium nuts that
fall free from the husk at harvest. The kernels should ideally be free of fibre.
Locations with less than ideal growing conditions (e.g. Class 3 soils, exposed to hot, dry winds, cool
summer temperatures, very hot dry summer climate) should plant varieties with small to medium nuts
such as Whiteheart, Tonda Romana or Tonda di Giffoni.
Orchard Management
Orchard management should aim to minimise stress on the tree during the main nut fill period from mid
December to March.
Use soil tests and leaf analysis to maintain optimum soil fertility.
Ensure that soil moisture levels are adequate
Keep trees well pruned to maintain adequate levels of light throughout the canopy.
Keep the orchard floor clean and free of debris. Collect or mulch all debris and old nuts well before
harvest.
Maintain control programmes for rats and mice.
Harvest
Do not leave nuts on the ground for more than one month after nut fall.
Harvest more frequently if leaf fall occurs while the nuts are falling, if regular rainfall keeps the soil
and nuts wet, or if many nuts are falling in husks (especially if husks are not completely dry).
Wash nuts immediately and rinse in sterilizing solution (e.g. sodium hypochlorite). Scrubbing may be
necessary if shells are coated with silt or clay.
Dry immediately. For small scale growers, nuts can be dried in shallow layers on racks (stir
frequently) to a minimum of 10-12% moisture before bagging in onion bags for final drying to 6%
moisture. Forced air drying systems should not use temperatures over 35˚C.
Store in a dry cool room (air humidity less than 65%, temperature less than 20˚C) free of any other
product that may contaminate the nuts. Hazelnuts will absorb odours if other strong smelling products
are stored in the same room.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Establishing an Orchard Page 1 of 7
Guidelines for Growing Hazelnuts in New Zealand
Bulletin 5: Establishing a hazelnut orchard
Murray Redpath. May 2016
Introduction
The foundation for successful hazelnut
growing is laid when the orchard is
established. Landowners intending to grow
hazelnuts commercially should use accurate
and up-to-date information from local and
national sources to guide them through the
establishment phase. Information required
includes:
suitable varieties for the targeted market
and orchard location
suitable pollinisers for the variety selected.
suitable tree spacing for the selected
varieties and local growing conditions.
shelter requirements.
suitable species for the orchard floor.
irrigation requirements and regulations.
soil characteristics.
Selection of varieties and pollinisers are
covered in Bulletins 2 and 3 of this series.
All major site development (shelter
establishment, drainage, ground preparation,
irrigation installation) should take place well
before the orchard is planted. Lime and any
potassium and magnesium requirements
should be added during ground preparation so
they can be cultivated into the soil.
Pastures on livestock farms are designed to
maximise grass growth. If this land is
converted to orchards this can lead to high
mowing costs, so slower growing grass
species such as fescues are frequently used.
Herbal leys have been used in some organic
orchards – these must be cut very low to
ground just prior to harvest.
Shelter
Hazels are easily damaged by strong winds,
especially when combined with low humidity
and high temperatures. Young plants will
struggle to grow satisfactorily in poorly
sheltered locations, leading to stressed plants
and increased problems with diseases.
Persistent winds through the main growth
period in spring and early summer can distort
the new growth and make it difficult to develop
a well balanced scaffold structure.
Fig. 1: Whiteheart plants two years after planting in
a well sheltered orchard on fertile soils. The nursery
plants were well grown 2 year old plants.
Fig. 2: Whiteheart plants two years after planting on
an exposed site on free draining stony soils. The
nursery plants were small one year whips and are
struggling in the exposed conditions.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Establishing an Orchard Page 2 of 7
Key considerations when planning shelter are:
Shelter should be sufficiently permeable to
allow air to filter through.
Deciduous species will maximise air flow
for pollen dispersal during winter.
Fast growing species like poplars and
willows have aggressive root systems that
may require regular root pruning to
prevent them competing for water and
nutrients.
Ideally shelter should be planted at right
angles to the direction of the predominant
damaging winds.
A shelter belt will provide protection for a
distance up to 10 to 15 times its height.
Depending on local wind conditions and
shelter species selected, shelter rows will
need to be 60 to 100 metres apart.
Shelter rows should be regularly trimmed
to maintain a narrow hedge shape with
foliage retained to ground level.
In dry regions, shelter may need to be
irrigated to prevent drought induced leaf
fall before or during harvest.
Shelter should be established several years
prior to planting the hazels to ensure the new
plants are adequately protected. Seek local
advice on suitable shelter species and layouts
for your region.
Irrigation
Locations with an annual rainfall over 900 mm
well distributed up until February may not
require irrigation, especially on deep silt or clay
loam soils. Locations that experience
prolonged periods of dry weather between
November and the end of January should
install irrigation, especially if the soils are free
draining (sandy or stony). In summer, up to
5 mm of water per day may be required to
replace the evapotranspiration losses.
Drippers and microsprinkler systems are
commonly used in New Zealand hazelnut
orchards. Water moves rapidly down through
free draining soils so microsprinklers should be
preferred on these soils to ensure that an
adequate area of the root zone is irrigated.
Young trees benefit from regular watering over
the first 2 years, even in climates where
permanent irrigation may not be necessary. If
permanent irrigation is not required, short-term
solutions such as tractor towed water tanks or
temporary hose and sprinkler systems may be
suitable.
Water regulations very between regions so
consult local irrigation experts and your
Regional Council for advice on regulatory
requirements and suitable irrigation options
Orchard layout
The design of the orchard needs to consider
the space needed by machinery used in
orchard management, the vigour of the
varieties used, expected growth rates for the
selected varieties, and the need to provide
adequate pollen to the cropping trees.
Tree spacing
The main intention of spacing decisions should
be to grow sufficient canopy to produce at
least 1 tonne per hectare by the sixth year and
2.5 tonnes per hectare by the eighth year.
Modern hazelnut orchards use high density
planting to maximise early returns. Usually
every second tree is removed in year 11 to 15
when the canopy closes in. Alternatively,
growers may choose to implement pruning
regimes that limit the canopy size of each tree.
The distance between tree rows must allow
efficient harvesting. This may mean
evaluating harvesting options before the
orchard is even planted and basing the inter-
row distance on the harvesting width of the
selected machinery. The distance needed to
easily turn the equipment at the end of the
rows also needs to be considered. Self
propelled harvesters or harvesters mounted on
the front of the tractor are likely to need less
room on the headlands than towed harvesters.
At least 5 metres is required; some equipment
may need up to 8 metres to turn adequately.
The distance between rows is also important
to maintain adequate light into the base of the
productive canopy. To maintain light in the
inter-row space, rows need to be one metre
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Establishing an Orchard Page 3 of 7
apart for every metre of eventual tree height.
In general, rows running in a north-south
orientation enable most efficient use of
sunlight.
A low vigour variety like Whiteheart is usually
grown in rows 4 to 4.5 metres apart in regions
like Canterbury with slow growth rates, where
the trees will take at least 10 years to reach
4.5 metres in height. By contrast, Whiteheart
would need rows spaced 5 metres apart in
Nelson to maintain the same light levels at the
tenth year (Figs. 3 and 4).
The same factors influence the distance
between trees within the row. Whiteheart trees
are commonly planted 2 to 3 metres apart
within the row in Canterbury orchards but need
to be spaced 3 to 4 metres apart where growth
rates are higher.
Varieties with a spreading branch structure,
like Ennis and Barcelona, need greater
distances between rows, and between trees
within the row, than varieties with an erect
branch structure like Whiteheart or Tonda di
Giffoni (Figs. 5 and 6).
Fig. 3: Ten year old Whiteheart trees in Canterbury
spaced at 5 metres by 2 metres yielding about 1
kilogram per tree or 1 tonne per hectare. The
canopy only occupies about 20% of the optimum
canopy volume for this spacing. To reach the
targeted crop volumes in these growing conditions,
the trees need to be spaced at 3 metres by 2
metres, too close for most harvesting equipment. A
more vigorous variety that can reach the optimum
canopy size by the eighth year may be required.
Fig. 4: Ten year old Whiteheart trees in Nelson
spaced at 5 metres by 3 metres yielding about 3
kilograms per tree or 2 tonnes per hectare. These
trees are meeting along the rows but still have room
to grow into the space between the rows.
Fig. 5: Seven year old Ennis trees in Blenheim
spaced at 5 metres by 5 metres, yielding over 6
kilograms per tree or 2.4 tonnes per hectare.
Optimum canopy development was reached by the
ninth year and major pruning was required by year
11.
Fig. 6: Thirteen year old Whiteheart trees in the
same orchard spaced at 5 metres by 4 metres,
yielding 3 to 4 kilograms per tree (1.5 to 2 tonnes
per hectare). Canopy has not yet reached the
volume of the 7 year old Ennis. At seven years old,
the trees were producing just over 1 kilogram per
tree or 500 kg per hectare. Whiteheart is a low
vigour variety and has grown at less than half the
rate of the Ennis trees. To achieve the targeted
yield, spacing needs to be 4.5 by 2 metres.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Establishing an Orchard Page 4 of 7
To calculate the number of trees required,
divide the available planting area by the
distance between the rows x distance between
the trees in the row. When calculating the
available planting area of a block, remember to
deduct the area used for headlands and land
adjacent to the shelter.
For example, a 1 hectare block with 5 metre
headlands and rows 5 metres in from the
shelter rows has 8100m2 of planted area. At a
4.5 by 3 metre spacing, this requires 600
plants:
8100 ÷ ( 4.5 x 3 ) = 600
planted area (row spacing tree spacing)
The table below gives the number of trees per
planted hectare required for common hazel
spacing options.
Table 1. Typical tree spacing and tree numbers required
Plant spacing No. of trees/ha.
4.5 m x 2.0 m 1111
4.5 m x 3.0 m 740
5 m x 3 m 666
6 m x 4 m 416
Thinning
Thinning the orchard when the canopy closes
involves removing every second tree in a
triangular pattern (see Fig. 7). This method
maximises the distance between the trees
after thinning. For example, thinning a 6 metre
by 3 metre spacing (used for vigorous varieties
like Barcelona) will result in 6 metres between
trees within the rows and 6.7 metres to trees in
adjacent rows.
P - X - X
- X - P -
X - X - X
- X - X -
X - X - X
- X - X -
P - X - X
- X - P -
X - X - X
Fig 7. Typical pattern for thinning orchards at
canopy closure, using a 6 metre by 3 metre orchard
spacing as an example. X = crop trees retained;
– = crop trees removed; P = polliniser trees.
Polliniser distribution
Overseas research has shown that pollen
density diminishes at 18 to 20 metres from the
source. Pollinisers need to be placed in
orchards so that no tree is more than 20
metres from a polliniser.
There are two main methods of spacing
pollinisers through the orchard. Some growers
prefer to plant rows of pollinisers every 20
metres or so through the orchard (Fig. 8). This
system has advantages during harvest as all
polliniser nuts are in specific rows. The second
method places pollinisers throughout the
orchard in a staggered pattern. In Oregon, the
pattern has pollinisers placed every third or
sixth tree (depending on in-row tree spacing)
in every third row (Fig. 9).
If thinning is planned, then care must be taken
at planting to ensure that pollinisers are not
placed in positions where they may be
removed during the thinning operation.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Establishing an Orchard Page 5 of 7
Pe X X X X Pe X X X X Pe X X X X Pe
Pm X X X X Pm X X X X Pm X X X X Pm
Pl X X X X Pl X X X X Pl X X X X Pl
Pe X X X X Pe X X X X Pe X X X X Pe
Pm X X X X Pm X X X X Pm X X X X Pm
Pl X X X X Pl X X X X Pl X X X X Pl
Pe X X X X Pe X X X X Pe X X X X Pe
Pm X X X X Pm X X X X Pm X X X X Pm
Pl X X X X Pl X X X X Pl X X X X Pl
Pe X X X X Pe X X X X Pe X X X X Pe
Fig. 8: Orchard layout using specific polliniser rows. X = main variety; Pe = early polliniser; Pm = mid season
polliniser; Pl = late polliniser.
Pe X X X X X Pm X X X X X Pl X X
X X X X X X X X X X X X X X X
X X X Pl X X X X X Pe X X X X X
X X X X X X X X X X X X X X X
X X X X X X X X X X X X X X X
X X X X X X X X X X X X X X X
Pm X X X X X Pl X X X X X Pe X X
X X X X X X X X X X X X X X X
X X X Pe X X X X X Pm X X X X X
X X X X X X X X X X X X X X X
X X X X X X X X X X X X X X X
X X X X X X X X X X X X X X X
Pl X X X X X Pe X X X X X Pm X X
Fig. 9: Orchard layout with pollinisers spaced throughout the orchard (based on a 6 x 3 metre orchard spacing).
X = main variety; Pe = early polliniser; Pm = mid season polliniser; Pl = late polliniser.
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Establishing an Orchard Page 6 of 7
Planting
Nursery stock
Good quality trees from the nursery are
essential for establishing high yielding
orchards. A strong, well balanced root system
is necessary for rapid establishment and
strong even growth. Nursery stock should
have a minimum stem diameter of about
10 mm at the base of the plant and a minimum
height of 800 to 1000 mm.
Most hazelnut plants are propagated by
mound layering using stool beds. This
produces a rooted sucker or whip that is the
same as the parent tree. Some varieties do not
easily establish roots using this method and
are sold as grafted plants. Alexandra, one of
the main late polliniser varieties used in New
Zealand, is usually sold as a grafted plant.
Plants are often sold as one year whips
straight off the stool beds. These are suitable
for planting in well prepared sites with
excellent shelter. Roots on one year whips are
soft and easily damaged, and care must be
taken during shipping and planting. Two year
old plants are more robust and should be used
where conditions are less than ideal.
Planting
Hazels are deciduous trees and are planted
over winter when dormant. Hazel roots grow
through the winter whenever soil temperatures
are above 4.5°C so planting as early as
possible enables the plants to develop a
working root system before bud burst.
Ensure that the roots are kept moist at all
times. If trees cannot be planted immediately,
heel them into well cultivated soil or sawdust.
Holes should be dug slightly larger than the
size of the tree roots. Trim any damaged or
long roots. Spread the roots out in the bottom
of the hole, add soil and give the roots a gentle
shake to ensure the soil is distributed among
the tree roots. Fill the hole and gently firm the
soil around the tree. Ensure that the top roots
are below the soil surface allowing for some
settling of the soil.
Large orchards are often planted using tree
planting machines. Care must be taken with
plant preparation when using planting
machines to ensure that roots are not swept
back along the line of the furrow. Roots need
to be trimmed to ensure they are not swept
upwards when moving through the machine. It
may be beneficial to plant slightly deeper than
the final depth and pull the plants up gently to
straighten any bent roots.
Trees should not need to be staked if the site
has adequate shelter.
Fig. 10: Planting with a tree planter.
Post-planting management
Protection
Trunks of young hazelnut trees are susceptible
to sunscald and frost damage in the first few
years after planting. Painting the stems with a
diluted white water based paint helps to
protect the trunk. The paint can be diluted up
to 50% (equal volumes of water and paint).
Paint the stems right down to just below the
soil surface to allow for soil settling.
Plastic tree guards and spray guards are often
used to protect the trunks of young trees.
These provide shade to the lower trunk,
Guidelines for Growing Hazelnuts in New Zealand – Bulletin 5: Establishing an Orchard Page 7 of 7
protection from spray drift from herbicides
used down the rows and protection from attack
by rabbits and hares. However, the guards
create a warm moist environment at the base
of the tree and this may provide ideal
conditions for bacterial blight. Control of
suckers growing inside tree guards is also
more time consuming.
Weed control
It is important to control weeds for at least the
first three years after planting, to minimise the
competition for water and nutrients.
Application of good quality mulch 5 to 10 cm
deep helps to retain soil moisture and assists
with weed control close to the plants. Keep the
mulch away from the lower trunk.
Pruning young trees
Young trees need to be pruned back to
compensate for damage to the roots during
transplanting. Cut the trees back to 70 to
120 cm high. Leave 4 to 6 buds at the top of
the whip and carefully rub out the remaining
buds lower on the stem. Spray the stem with
copper to help protect any wounds from
infection with bacterial blight.
Tree shaping depends on whether growers
choose to grow a multi-stemmed bush or a
single trunk tree. Hazels are naturally a
suckering plant forming multi-stemmed bushes
and this growth form is used in commercial
orchards in Turkey and parts of Italy where 4
to 6 stems are retained to form the productive
canopy. Research indicates that there is no
significant difference in yields between multi-
stemmed and single trunk trees.
Most modern orchards grow hazels as a single
trunk trees because it allows easier access for
field operations and machinery. Nuts can also
become trapped within the base of multi-
stemmed plants.
If a single stem tree is planned, the main
object of pruning in the first few years is to
create an open vase shape with 3 to 5 main
scaffold branches.
After the first year’s growth, select the limbs
that will become the main scaffold branches.
Ideally choose limbs which are evenly spaced
around the tree, with 10 to 15 cm of vertical
separation. Remove all other limbs and
shorten the selected limbs to 60 – 80 cm,
cutting back to an outwards facing bud. If there
is insufficient growth in the first year to select
the required number of scaffold branches, then
remove all unwanted shoots to stimulate new
growth and select the scaffold branches in the
second winter.
Once the main scaffold branches are selected,
pruning should be restricted to removing
shoots that compete with the scaffold
branches. This includes strong vertical shoots,
side branches that threaten to become more
dominant than the main scaffold branch, and
branches that cross over adjacent scaffold
branches.
The “Guidelines for Growing Hazelnuts in New Zealand” bulletins were produced by the Hazelnut
Growers Association of NZ with financial assistance from the Ministry for Primary Industries
Sustainable Farming Fund and the NZ Tree Crops Association.
Murray Redpath is Chairman of the Hazelnut Growers Association of NZ.
Photographs: Figs 1 to 6: Murray Redpath. Fig 10: Sarah Shore
Disclaimer
While the author has taken all reasonable skill and care in assessing the accuracy of the information in this report, none of the
organisations involved accepts any liability, whether direct, indirect or consequential, arising out of the provision of information
within this report.